The problem of growing Nephs is that mold takes over before you can grow anything. if it need to be high and acidic can't you use coffee? A mixture of Coir, Verm, Peat and perlite hydrated in diluted coffed and water. Coffee is high and acidic. and to take care of the problem of mold. put it in a microwave safe tubberware and microwave it for 5 minutes. that'll kill any mold spores or contamination. then you can leave the lid on the tubberware to hold humidiy and keep out airborn contaminates. it sounds like it'll work.